Data Viz Principles and Practices

Stat 365: Statistical Communication

Monday, May 1st1

Today we will…2

  • Gestalt Principles
  • Perception of Data Viz
  • Case Study
  • Redesign the Graph

The gestalt effect

  • gestalt = form or pattern

  • Gestalt philosophy: “The whole is other than the sum parts” -Kurt Koffka

  • Gestalt principals: Predictable ways by which we organize sensory information.

Law of proximity

We interpret objects that are close to each other as a group

Law of similarity

We interpret objects that are visually similar to each other as a group

Law of closure

When parts of a picture are missing, we fill in the visual gap

Law of symmetry

We perceive objects as being symmetrical, arranged around a center point

Law of common fate

We group objects that we percieve to be moving along the same path

Law of continuity

We tend to group objects along the smoothest path

Gestalt Hierarchy

Effect Graphs
Enclosure Facets
Connection Lines
Proximity White space
Similaryt Color/shape

Perception

Some things are processed slower1

Other’s are incredibly fast1

Fast = “pre-attentive processing”

  • Things that happen in <200ms of visual stimulation
  • Performed in parallel across the entire visual field

Get ready

What did you see?

“An understanding of what is processed pre-attentively is probably the most important contribution that visual science can make to the data visualization” (Ware, 2004, p. 19)

Pe-attentive features1

Color (hue)

Orientation

Intensity

Clustering

Size

Length

and more!

Pre-attentive processing facilitates:

  • Target detection (Presence or absence)
  • Boundary detection / grouping
  • Region tracking
  • Counting and estimation

Attentive Counting1


Pre-attentive Counting1


Graphical Perception

Cleveland and McGill, 1984

The following are the 10 elementary tasks in Figure 1, ordered from most to least accurate:

  1. Position along a common scale
  2. Positions along nonaligned scales
  3. Length, direction, angle
  4. Area
  5. Volume, curvature
  6. Shading, color saturation

Magnitude estimation1

Magnitude estimation1

Magnitude estimation1

“Apparent” magnitude1

Implications for Practice

  1. Know how we perceive groups

  2. Know that we perceive some groups before others

  3. Design to facilitate and emphasize the most important comparisons

Case Study on Gestalt Principles[^via Silas Bergan]

body_loc swim_loc time avg_temp
cheek indoor pre 95.2
cheek indoor post1 84.3
cheek indoor post2 86.2
elbow indoor pre 95.4
elbow indoor post1 89.1
elbow indoor post2 91.4
palm indoor pre 91.7
palm indoor post1 84.1
palm indoor post2 89.3
pec indoor pre 93.3
pec indoor post1 84.2
pec indoor post2 87.6
cheek outdoor pre 76.0
cheek outdoor post1 53.0
cheek outdoor post2 61.6
elbow outdoor pre 92.5
elbow outdoor post1 61.9
elbow outdoor post2 80.6
palm outdoor pre 74.6
palm outdoor post1 48.6
palm outdoor post2 58.5
pec outdoor pre 87.2
pec outdoor post1 52.9
pec outdoor post2 69.6

4 body locations

x 2 swim locations

x 3 time points

= 24 body temperature averages

Questions

Client Question

Does the body temperature recovery as recorded at the four body points depend on water temperature?

Consultant Questions

What are the elemental groupings? (What belongs together?)

How do we design for effective emphasis?

What are the elemental groupings?

Does the body temperature recovery as recorded at the four body points depend on water temperature?

What are the elemental groupings?

Does the body temperature recovery as recorded at the four body points depend on water temperature?

What are the elemental groupings?

Most elemental

  1. Single time average
  2. Time Triplets
  3. Swim locations (aka water temp)
  4. Body locations

Least elemental

Does the body temperature recovery as recorded at the four body points depend on water temperature?

Redesign the graph

“New Census Data Show More Americans Are Tying the Knot, but Mostly It’s the College‐Educate”- Pew Reserach”

The graph is meant to demonstrate that the 2011 to 2012 increase observed in total new marriages was driven primarily by an increase in those having a bachelor’s degree or more.

To do

Data and Methods + Table

  • due Thursday, 5/4
  • You will need to include your statistical methods.
  • REPRODUCIBILITY! Document EVERYTHING!
  • Read CwD 3.4: Tracking the Analysis

Practice in Tableau

  • Submit URLs: due Monday, 5/1 at 11:59pm